Yahoo General Counsel Michael Callahan, in testimony Tuesday to a U.S. congressional committee, defended his company's advertising partnership with Google Inc and said Yahoo would not be sold off piecemeal on terms that disadvantage Yahoo stockholders.

"Microsoft... has turned to activist shareholder Carl Icahn, in the apparent hope that this will force a fire sale of Yahoo's core strategic search business," Callahan said at a hearing before the Senate Judiciary Committee's antitrust subcommittee.

Icahn is leading a proxy campaign to dump Yahoo's current management and board at the August shareholder meeting.

Google, with more than 60 percent of the Web search market, and Yahoo, with 16.6 percent, announced a deal on June 12 that would allow Yahoo to place Google advertisements on its site and collect the revenue.

The Yahoo-Google partnership was widely seen as an effort by Yahoo to fend off Microsoft's on-again, off-again efforts to buy all or part of Yahoo. Microsoft has criticized the partnership as an anticompetitive threat to advertisers and consumer privacy.

Microsoft's most recent offer to acquire Yahoo's search business was rejected Saturday evening by Yahoo.